It is difficult to reduce the size of keyboards widely used for input devices of computers, for the structure with a plurality of massed keys, including Korean/English character keys, number keys, symbol keys, and function keys. Even if they are manufactured in a small size, it is difficult to input data, due to the size of the general user's hands.
In particular, for portable microcomputers rapidly rising in demand in recent years, such as UMPC, a display of 10 inches or less is usually mounted and the integral keyboard mounted in the main body is provided in a very small size, such that the it is inconvenience to use the computer and is required to improve the structure of the keyboard. Removable keyboards that are connected by USBs (Universal Serial Bus) etc. are used to solve the inconvenience of the integral keyboards; however, it is inconvenience to carry the removable keyboards and required to be careful of handling them because there is possibility of loss.
In consideration of improvement of the keyboard structure, a keyboard having a structure in which a housing is formed at both side of the main body of a keyboard to accommodate sub-keyboards and the sub-keyboards are taken out and connected to the sides of the main body of the keyboard for use is disclosed in Korean Utility Model Publication No. 1995-25665. This sectional keyboard, however, the terminals for electric connection between the main body of the keyboard and the sub-keyboards are worn or exposed to foreign substances due to frequent connection/disconnection, such that bad connection may be caused.
For another example, keyboards that can increase in size, using foldable structure is disclosed in Korea Patent Publication No. 1998-28435 (Portable computer having a foldable keyboard) and Korea Utility Model Publication No. 1999-001643 (Foldable keyboard structure for portable computer). The keyboards disclosed in the documents use a foldable structure for folding the parts of the keyboards and developing them for use. However, this structure increases the entire thickness when being folded, such that it is difficult to achieve a thin portable computer.